This invention relates to motor vehicle body structure, and more particularly to a pickup truck box construction.
Pickup truck boxes have traditional been made of stamped and/or roll-formed steel components that are welded together and integrated into the pickup truck body. Steel pickup truck boxes are provided with an aesthetic/protective finish coating or paint that prevents the steel from coming in direct contact with moisture and other corrosive agents. However, without supplemental protection, the finished coating on the pickup truck box can become scratched, chipped or otherwise damaged during loading and unloading of cargo and due to shifting of cargo in the pickup truck box. Scratches, chips, and other discontinuities in the finish coating expose the steel to moisture and other corrosive agents, ultimately leading to corrosion of the pickup truck box. Also, a pickup truck box that is not provided with supplemental protection can be dented during loading, unloading or shifting of cargo.
The use of a plastic pickup truck box liner to protect the pickup truck box and the finish coating on the box against damage have become very popular. However, a problem with preformed plastic liners is that they tend to trap moisture between the liner and the pickup truck box. This eventually promotes corrosion of the pickup truck box, especially along seams where the steel components of the box are joined together. Consequently, the preformed plastic pickup truck box liners can add to the cost of the vehicle without fully protecting the pickup truck box against corrosion.
An alternative to preformed pickup truck box liners is a sprayed on plastic liner that is applied in fluid form to the surfaces of the pickup truck box and cured to form a solid liner that is bonded directly to the surface of the box, whereby gaps between the liner and the box are eliminated so that moisture cannot be trapped between the liner and the box. Therefore, the sprayed on plastic liners provide enhanced corrosion protection as compared with preformed plastic liners. However, known sprayed on liners are susceptible to degradation due to exposure to ultraviolet radiation and, as a result, can exhibit deterioration of desired aesthetic and functional characteristics.
More recently, motor vehicle manufacturers have offered pickup trucks with a one-piece pickup truck box made of a glass fiber reinforced plastic. The reinforced plastic pickup truck boxes have many advantages over the traditional steel boxes, including reduced weight which in turn provides improved fuel economy, and an inherent resistance to impact and corrosion which eliminates the need for a protective liner.
The known reinforced plastic pickup truck boxes are made by a relatively expensive and complicated process in which a glass fiber preform having the desired complex three-dimensional shape of the pickup truck box is first prepared by a directed fiber preforming process in which a flow of chopped fibers is drawn by vacuum against a foraminous screen having a shape corresponding to that of the preform. The preform is then removed from the foraminous screen and laid on a mold having a shape corresponding to the preform. The mold is then closed and a plastic resin is injected under pressure into the closed mold. The resin flows through the fiber preform and around the individual glass fibers to completely fill the mold and surround the fibers. Thereafter, the resin is cured or solidified to form a unitary glass fiber reinforced pickup truck box.
In addition to being complicated and expensive, the known process can lead to the production of pickup truck boxes in which the glass reinforcing fibers are not uniformly distributed throughout the plastic. Due to the relatively deep draw depth of a pickup truck box, the glass fibers of the preform can be pulled or dragged along interior surfaces of the mold when the mold is closed. Fibers can also be carried by the resin during the resin injection step. Movement of the glass fibers either during closing of the mold or during injection of the resin can lead to a non-uniform distribution of the fiber reinforcement in the resin matrix, whereby the finished pickup truck box may have resin rich regions and resin lean regions. The resin rich regions have a reduced reinforcing fiber content and, consequently, have inferior mechanical properties. These inferior mechanical properties can lead to potential structural failures if used and/or high rates of product rejection.
Another problem associated with the known fiber reinforced plastic pickup truck boxes is that because the walls of the pickup truck box are perpendicular, or at least very nearly perpendicular, to the floor of the box, the finished unitary boxes cannot be stacked in a space efficient nested arrangement. Therefore, costs associated with shipping the known fiber reinforced plastic pickup truck boxes from the manufacturer to the location where the pickup truck is assembled can be relatively high.
In the process and product of the present invention, a pickup truck box is made of a plurality of separately molded sections made of plastic and joined together with an adhesive. The plastic pickup truck boxes of this invention have the advantages of being lightweight, and inherently resistant to corrosion and impact damage, while also facilitating lower cost production techniques and reduced shipping costs due to better nesting and packing efficiency. The pickup truck box of this invention also exhibits improved mechanical properties and durability as compared with a conventional one-piece plastic liner due to more uniform distribution of fiber reinforcement.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.